The objectives of the proposed research aze four-fold. The first objective is to establish the role of AMP and ADP in the regulation of polypeptide synthesis in lysed rabbit reticulocytes. With 1 mM ATP and the CP/CPK energy regenerating system, 0.25 mM and 1 mM AMP inhibit polypeptide synthesis 41% and 72%, respectively. The Ki AMP is 300 uM. The polyribosome profiles were analyzed by sucrose density gradient centrifugation in the presence of 1 mM AMP. The shift to higher polysomes implies that translational inhibition occurs at polypeptide elongation. Removal of AMP with either AMP-nucleosidase or AMP-deaminase restores protein synthesis. The second objective involves the role of poly(ADP-ribosylation) in the chromatin structure of HeLa cells. To determine these changes in poly(ADP-ribose), HeLa cells are treated with human fibroblast interferon. The data show that in asynchronously or synchronously grown HeLa cells, interferon (100 units/ml) stimulates the incorporation of (3H) thymidine into TCA insoluble material. This increase in the corporation of radioactivity is about the 200-300%. Similarly, there is also an increase in ADP-ribosylation. The nature of the increased incorporation of thymidine into acid insoluble material and the type ADP%ribosylation that occurs is under investigation. The third objective is concerned with the biosynthesis of the cyclopentene diol ring of Q base of tRNA. The primary effectin this study if focused on the isolation of the enzyme that will synthesize the Q base from GTP and glucose. This is being accomplished by the isolation of E. coli mutants which accumulate eitherbase Q or nucleoside Q. The fourth objective is concerned with the biosynthesis of e-ethylidene-azetidine-2-carboxylic acid in the polyoxins by S. cacaoi. The synthesis of (4S-3H,2-14C) isoleucine has been completed. Biosynthetic studies are now underway to determine which hydrogen on carbon-4 ir removed in the formation of the azetidine ring.